Christel Rousseau

Characterization of natural carious lesions by fluorescence spectroscopy at 405-nm excitation wavelength

We aim to characterize natural caries enamel lesions by fluorescence spectroscopy. Sixty human samples with natural noncavitated caries lesions on smooth surfaces were selected and classified into three groups: dull, shiny, and brown lesions. All the samples were analyzed externally at the natural surface and after hemisectionig internally at the center of the lesion. The lesions were excited with a 405-nm InGaN diode laser and the fluorescence was collected with a single grating spectrometer. Four emission bands (455, 500, 582, and 622 nm) are identified in both sound and carious regions. The area under each emission band is correlated with the total area of the four bands for the sound and carious regions. The detected fluorescence from natural and cut surfaces through the caries lesions is not statistically different for the shiny and dull lesion, but is different [analysis of variance (ANOVA) (p<0.05)] for brown lesion at all emission bands. At the 405-nm excitation wavelength, the area of the fluorescence bands at 455 and 500 nm differ statistically for natural carious lesions and sound tissue.

Development of fibre-optic confocal microscopy for detection and diagnosis of dental caries

We report on the development of a fibre-optics-based confocal imaging system for the detection and potential diagnosis of early dental caries. A novel optical instrument, capable of recording axial profiles through caries lesions using single-mode optical fibres, has been developed. The practical study illustrates that miniature confocal devices based around single-mode optical fibres may provide additional diagnostic information for the general dental practitioner.

The Effect of Dentine on Fluorescence Measurements of Enamel Lesions in vitro

This study aimed to determine the contribution of the underlying dentine and the enamel-dentine junction to measurements of mineral loss from enamel recorded using quantitative light fluorescence (QLF). Sixteen square blocks (5 × 5 mm) were cut from the labial surfaces of extracted bovine incisor teeth. A dental drill was used to remove dentine and the enamel-dentine junction from half of each specimen. All specimens were embedded in epoxy resin and ground to produce a smooth, flat enamel surface. Half of the enamel surface of the block, perpendicular to where the dentine had been removed, was demineralised for 72 h prior to undertaking QLF measurements from the enamel surface to compare fluorescence loss from different areas of the block. QLF readings taken from lesions with no underlying dentine or enamel-dentine junction were very similar to readings from lesions with underlying dentine. A comparison of the two data sets demonstrated a linear relationship with a gradient of 0.95 and a y intercept of –1.24 (r2 = 0.936). From these data, the underlying dentine and enamel-dentine junction did not influence mineral loss in enamel measured using QLF.

Application of a novel confocal imaging technique for the early detection of dental decay

In order to stop or prevent the progression of dental disease, early detection and quantification of decay are crucially important. Dental decay (caries) detection methods have traditionally involved clinical examination by eye, using probes and dental radiography, but up to 60% of lesions are missed. What the dentist requires is a cheap, reliable method of detection of early disease, ideally with information on the depth and rate of growth or healing. Conventional commercial scanning confocal microscopes are unsuitable for use on dental patients. We report on a fibre optic based confocal microscope designed for in vivo examination of caries lesions. The system utilizes a common fibre both as the source and to detect the reflected confocal signal. The initial system has been optimized using dielectric mirrors and the thickness of the stack has been measured with high precision. Dental samples have been examined and the system has been demonstrated to provide information on the depth and mineral loss of a lesion. Fibre optic microscopy (FOCM) demonstrates a practical route to developing an in vivo caries profiler. In this paper, the FOCM and its applications in caries detection are described and the potential of this scheme as a practical dental probe is discussed.

Blue-laser-diode-excited fluorescence spectroscopy of natural carious lesions

We report on the use of a blue laser diode to excite natural fluorescence from a range of dental samples. Sixty teeth with naturally occurring lesions were examined. The lesions were classified on visual inspection as falling into three classes as shiny lesions, dull lesions and brown lesions. The resulting fluorescence was then examined using a fibre optically coupled spectrometer in a series of wavelength bands. By examining the intensity ratios in the two wavelength bands 480-500nm and 620 to 640nm we were able to classify the lesion types and thus provide a quantifiable measurement of lesion types. This method has application for detection of dental caries as well as demonstrating potential application to evaluate lesions which may represent different degrees of caries activity.

Application of a fibre-optic confocal microscope to the detection of artificial enamel lesions

Abstract In recent years, fluorescence-based optical methods for detecting dental caries have been examined with some success. However, these methods do not explicitly assess the lesion depth, which may prove to be a useful indicator of the progression/regression of dental caries. The purpose of this study was to apply a newly developed fibre optic-based confocal microscope to the characterisation of artificial enamel lesions in their initial stages. Lesions were found to produce characteristic back-scattering signals, with an initial peak indicating the sample surface and a smaller secondary peak indicating the base of the lesion. Analysis of these signals showed that lesions from as little as 20 to over 100 μm deep could be detected. As the technique incorporates fibre optics to deliver the excitation light and collect the back-scattered light, it is suited to clinical application. Further work is needed to show that this method is applicable to detecting natural lesions in vivo.